public class UnlockableModel
{
    [BsonId]
    public Guid profileId { get; set; }
    public Dictionary<String, List<String>> entries { get; set; }
}

List<string> categories = new List<string> {"Test"};

var filter = Builders<UnlockableModel>.Filter.Eq(model => model.profileId, profileId);
var options = new FindOptions<UnlockableModel>
{
    Projection = Builders<UnlockableModel>.Projection.Expression(p => new UnlockableModel
    {
        profileId = p.profileId,
        entries = (p.entries != null) ? new(p.entries.Where(kvp => categories.Contains(kvp.Key))) : new()
    })
};

var result = await _unlockableCollection.FindAsync(filter, options);

var connectionString = "mongodb://localhost";
MongoClientSettings settings = MongoClientSettings.FromConnectionString(connectionString);
settings.LinqProvider = LinqProvider.V2;